Urban flood modeling with porous shallow-water equations: a case study of model errors in the presence of anisotropic porosity

Porous shallow-water models (porosity models) simulate urban flood flows orders of magnitude faster than classical shallow-water models due to a relately coarse grid and large time step, enabling flood hazard mapping over far greater spatial extents than is possible with classical shallow-water models. Here the errors of both isotropic and anistropic porosity models are examined in the presence of anisotropic porosity, i.e., unevenly spaced obstacles in the cross-flow and along-flow directions, which is common in practical applications. We show that porosity models are affected by three types of errors: (a) structural model error associated with limitations of the shallowwater equations, (b) scale errrors associated with use of a relatively coarse ∗Tel: +1 949 824 4327; fax +1 949 824 3672 Email address: [email protected] (Brett F. Sanders) URL: http://sanders.eng.uci.edu (Brett F. Sanders) UC Center for Hydrologic Modeling, Irvine, CA, USA Department of Civil and Environmental Engineering, University of California, Irvine, CA, 92697, USA Department of Earth System Science, University of California, Irvine, CA, 92697, USA NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA Université Montpellier 2, HydroSciences Montpellier, CC MSE, Place Eugéne Bataillon, 34095 Montpellier Cedex 5, France Preprint submitted to Journal of Hydrology October 25, 2014 *Revised Manuscript with no changes marked Click here to view linked References